The present invention relates generally to gas monitors for an enclosure. More particularly, the present invention relates to an assembly for attaching, with a quick disconnect coupling, a gas density monitor to an enclosure containing, for example, electrical switch gear.
In many electrical power components, a switch is used to control current flow through a conductor. Opening a current-carrying conductor may cause arcing, which may be harmful to the switch. To minimize arcing, such a switch is typically contained in an enclosure (e.g., a tank) and the enclosure is typically filled with an insulating gas. The gas minimizes arcing upon opening or closing a current carrying conductor.
In order to ensure that the gas will perform its insulating task as designed, it is important that the gas within the tank is maintained within a pre-selected density range. Since tanks may leak over time, allowing gas to escape from the tank, the density of the gas is usually constantly monitored by a gas monitoring system.
FIGS. 1A and 1B illustrate a prior art gas monitoring system. As illustrated in those Figures, a network of pipes 2 feeds the gas from each of the three tanks 3 back to a single density monitor device. As one might expect, if the density falls to an insufficient level, this design makes it difficult to determine the location (i.e., which tank is actually experiencing the leak) and exposes all of the circuit breakers to failure from a leak in a single tank. Moreover, the intricate piping network also creates more places for leaks to occur (e.g., at threaded connections in the network of pipes).
To overcome such a problem, a monitoring system may include one density monitor device coupled to each of the three tanks 3. In this manner, each tank is separately monitored and the need for some of the intricate piping is avoided. However, such a system typically includes traditional gas piping having threaded connections and this traditional gas piping is a source of much gas leakage.
One system of minimizing the amount of traditional gas piping is described in U.S. patent application Ser. No. 09/288,678 filed Apr. 9, 1999, entitled xe2x80x9cGas Density Monitor Assemblyxe2x80x9d. The system includes a valve that couples the tank to the gas density monitor. The system considerably reduces the amount of traditional gas piping by mounting the gas density monitor, via the valve, to the tank. Since the gas density monitor is mounted proximate to the tank, the amount of piping required is significantly reduced, thereby minimizing the chance for leakage. In addition, in one embodiment, the valve has a handle and the gas density monitor has a cover. The valve handle is configured such that when the monitor and cover are coupled to the valve, the valve is open. Also, the valve handle is configured to prevent the cover from being placed back on the gas density monitor when the valve is closed. In this manner, the system insures that a valve that was shut-off during testing is not inadvertently left shut-off when testing is complete. This system is a significant improvement over the previous art and provides reduced leakage and a way to insure that the valve is reopened after testing. However, the valve may inadvertently be left open during testing. If the valve is left open during testing, gas may escape from the tank.
Thus, there is a need for a low leak gas density monitoring apparatus that provides a fail-safe connection.
The present invention meets the above need for a fail-safe low leak gas density monitor by providing an assembly for monitoring the fluidic contents of a tank having a quick disconnect valve.
According to an aspect of the present invention, the assembly includes a monitor device, a quick disconnect fitting, and a monitor cover. The monitor device is coupled to the quick disconnect fitting such that fluidic pressure may pass through the quick disconnect fitting to the monitor device. That is, the quick disconnect fitting is coupled to the monitor device such that interior of the quick disconnect fitting is in fluidic communication with the interior of the monitor device. The quick disconnect fitting is adapted to be coupled to the quick disconnect valve of the tank, thereby allowing the fluidic contents of the tank to be in fluidic communication with the density monitor. The monitor cover is coupled to the monitor device, such that, when the quick disconnect fitting is coupled to the quick disconnect valve, the monitor cover is coupled to the tank.
The quick disconnect valve is closed when there is no corresponding quick disconnect fitting coupled to it. The quick disconnect valve is open when there is a corresponding quick disconnect fitting coupled to it. In this manner, the quick disconnect valve is always in the proper state and is therefore, fail-safe. That is, the valve automatically closes upon removal of the quick disconnect fitting and automatically opens upon coupling of the quick disconnect fitting. This provides a fail-safe valve, as well as provides little gas loss upon removal of the quick disconnect fitting.
According to another aspect of the present invention the quick disconnect valve is coupled to the tank with a double o-ring seal and the quick disconnect fitting is coupled to the quick disconnect valve with a double o-ring seal. The double o-ring seals provide a reliable robust sealing system, even if mounting bolts are not fully tightened.
According to a further aspect of the present invention, the monitor device cover is disposed over the monitor device and against the outside wall of the tank to maintain the monitor device at approximately the temperature of the tank, theoretically providing a more accurate estimation of gas density. In one embodiment of the invention, the monitor cover is coupled to the outside wall of the tank via a gasket.
Other features and advantages of the present invention are disclosed below.